Vehicle wheel assemblies of the live spindle type are currently known to those skilled in the art of vehicle wheel assembly design. U.S. Pat. No. 4,010,986 shows a typical live spindle design in which the spindle is journaled or mounted for rotation in a bore of a mounting component attached to the vehicle. Bearings are interposed between the mounting component and the spindle. A drive axle is inserted through a central bore or aperture in the spindle. Generally, the drive axle is threaded on one end and has a bearing retaining flange adjacent the opposite end. A nut on the threaded end is torqued down sufficiently to maintain the assembled components in the desired relationship and the axle is substantially rigidly affixed to the spindle so that the spindle and axle must rotate together at all times and no axial movement of the axle relative to the spindle is allowed. The prior art axles of the live spindle type do not permit axial movement of the axle relative to the spindle to relieve stresses imposed on the drive train components which drive the axle.
The prior art live spindle designs generally provide acceptable constructions in those applications where the axis of the drive shaft does not deflect from a fixed plane. A typical example of such constructions is the conventional rear drive axle in which a rigid tubular housing envelopes the drive axle shaft and maintains a single plane and a single swing axis from one rear wheel to the other as well as a fixed length of the drive axle to a different gear or other power source.
In motor vehicles having independent suspension each independently suspended wheel can move separate from the other wheels. Consequently, in independently suspended drive wheels the drive shaft centerline is required to pass through more than one plane. This movement requires universal joints and sliding joints, generally of the telescoping type, which enable the drive train to deflect transversely and lengthen and shorten axially.
Additionally, independently suspended wheels which also are articulated to serve as steerable wheels must move through a suspension arc and also are subject to movement about an inclined axis dictated by the steering geometry. These compounded movements cause the drive train universal joints to constantly seek to center about a multiplicity of intersecting planes when the wheel undergoes suspension deflection and simultaneous steer turning.
The presence of normal manufacturing tolerances creates additional need for the drive train to seek transverse and axial adjustments.
The inability of the drive train and universal joints to readily properly adjust or position itself in response to a suspension deflection and/or steer movement creates imbalanced or eccentric rotation of the drive train. The consequences of imbalanced drive train rotation and/or misalignment generally are vibrations. These vibrations may range from being small in amplitude and of short duration, but irritating, to so severe that components such as universal joints are ruined.
Furthermore, in conventional live spindle constructions the ability of the wheel to support the vehicle and be steerable is dependent upon the structural integrity of the stub axle, which maintains the spindle in the hub. If the stub axle breaks the wheel may be detached from the vehicle and consequently no longer support it. If the wheel is also articulated breakage of the stub axle would cause the vehicle to be substantially unsteerable.